Bidirectional alterations in antibiotics susceptibility in Staphylococcus aureus-Pseudomonas aeruginosa dual-species biofilm.

In mixed infections, the bacterial susceptibility differs significantly compared to monocultures of bacteria, and generally the concentrations of antibiotics required for the treatment increases drastically. For S. aureus and P. aeruginosa dual species biofilms, it has been numerously reported that P. aeruginosa decreases S. aureus susceptibility to a broad range of antibiotics, including beta-lactams, glycopeptides, aminoglycosides, macrolides, while sensitizes to quinolones via secretion of various metabolites. Here we show that S. aureus also modulates the susceptibility of P. aeruginosa to antibiotics in mixed cultures. Thus, S. aureus-P. aeruginosa consortium was characterized by tenfold increase in susceptibility to ciprofloxacin and aminoglycosides compared to monocultures. The same effect could be also achieved by the addition of cell-free culture of S. aureus to P. aeruginosa biofilm. Moreover, similar increase in antibiotics efficacy could be observed following addition of S. aureus suspension to the P. aeruginosa mature biofilm, compared to P. aeruginosa monoculture, and vice versa. These findings open promising perspectives to increase the antimicrobial treatment efficacy of the wounds infected with nosocomial pathogens by the transplantation of the skin residential microflora.

Unraveling the Molecular Mechanism of Selective Antimicrobial Activity of 2(5H)-Furanone Derivative against Staphylococcus aureus.

Staphylococcus aureus causes various infectious diseases, from skin impetigo to life-threatening bacteremia and sepsis, thus appearing an important target for antimicrobial therapeutics. In turn, the rapid development of antibiotic resistance and biofilm formation makes it extremely robust against treatment. Here, we unravel the molecular mechanism of the antimicrobial activity of the recently unveiled F105 consisting of three pharmacophores: chlorinated 2(5H)-furanone, sulfone, and l-menthol moieties. F105 demonstrates highly selective activity against Gram-positive bacteria and biofilm-embedded S. aureus and exhibits low risk of resistance development. We show explicitly that the fluorescent analogue of F105 rapidly penetrates into Gram-positive bacteria independently of their cell integrity and viability and accumulates there. By contrast, Gram-negative bacteria remain impermeable and, therefore, insusceptible to F105. Apparently, in bacterial cells, F105 induces reactive oxygen species (ROS) formation and nonspecifically interacts with a number of proteins, including ROS-utilizing ones. Using native and 2D PAGE, we confirm that F105 changes the charge of some proteins by either oxidation or direct interaction with them. Therefore, it seems justified to conclude that being simultaneously a ROS inducer and damaging proteins responsible for ROS utilization, F105 impairs the cellular anti-ROS defense representing a prospective ROS-inducing antibacterial agent.

Targeting microbial biofilms using Ficin, a nonspecific plant protease.

Biofilms, the communities of surface-attached bacteria embedded into extracellular matrix, are ubiquitous microbial consortia securing the effective resistance of constituent cells to environmental impacts and host immune responses. Biofilm-embedded bacteria are generally inaccessible for antimicrobials, therefore the disruption of biofilm matrix is the potent approach to eradicate microbial biofilms. We demonstrate here the destruction of Staphylococcus aureus and Staphylococcus epidermidis biofilms with Ficin, a nonspecific plant protease. The biofilm thickness decreased two-fold after 24 hours treatment with Ficin at 10 µg/ml and six-fold at 1000 µg/ml concentration. We confirmed the successful destruction of biofilm structures and the significant decrease of non-specific bacterial adhesion to the surfaces after Ficin treatment using confocal laser scanning and atomic force microscopy. Importantly, Ficin treatment enhanced the effects of antibiotics on biofilms-embedded cells via disruption of biofilm matrices. Pre-treatment with Ficin (1000 µg/ml) considerably reduced the concentrations of ciprofloxacin and bezalkonium chloride required to suppress the viable Staphylococci by 3 orders of magnitude. We also demonstrated that Ficin is not cytotoxic towards human breast adenocarcinoma cells (MCF7) and dog adipose derived stem cells. Overall, Ficin is a potent tool for staphylococcal biofilm treatment and fabrication of novel antimicrobial therapeutics for medical and veterinary applications.

Nano-labelled cells-a functional tool in biomedical applications.

Nanotechnology offers an unprecedented number of opportunities for biomedical research, utilizing the unusual functionalities of nanosized materials. Here we describe the recent advances in fabrication and utilization of nanoparticle-labelled cells. We present a brief overview of the most promising techniques, namely layer-by-layer polyelectrolyte assembly on cells and intracellular and extracellular labelling with magnetic nanoparticles. Several important practical application of nanofucntionalized cells, including tissue engineering and tumour therapy, are reviewed.